Adding elements in the array on the basis of an object

Question


const prefer={"cs":{"c1":true,"c2":true,"c3":false,"c4":true}}

setArray((prevArray)=>{
      return prevArray.filter(function(array){
        //code here
      })
    });

I want to set array on the basis of prefer object, like if c1 is true then is want to add it in the array Do I need to initialize the array too? In above example array=["c1","c2","c4"] . Also do we need filter method or can we use some other method

Does this answer your question? [Filter object properties by key in ES6](https://stackoverflow.com/questions/38750705/filter-object-properties-by-key-in-es6) — Vivek Molkar, Mar 28 '20 at 06:33

score 1 · Accepted Answer · answered Mar 28 '20 at 06:31

1

You can use for-in loop to iterate map/object

const prefer = { c1: true, c2: true, c3: false, c4: true };
    
    let arr = [];
    for (let key in prefer) {
      if (prefer[key]) arr.push(key); // modify how u want to save
      
       // arr.push({ [key]: prefer[key] }); // if u want key and value
    }
    console.log(arr);

answered Mar 28 '20 at 06:31

xdeepakv

7,835
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I like this. Short and sweet. I'll leave my long and bitter answer up just for reference. – thingEvery Mar 28 '20 at 06:41
haha, u are iterating 2 time, once to get keys and filter. clean but verbose and low performance – xdeepakv Mar 28 '20 at 06:48
You change `prefer` with `prefer.cs` – xdeepakv Mar 28 '20 at 18:35

score 1 · Answer 2 · answered Mar 28 '20 at 06:34

1

You can express it as follows,

const prefer = { "c1":true, "c2":true, "c3":false, "c4":true }

const output = Object.entries(prefer)
  .filter(([, value]) => value)  // !!value or Boolean(value) to coerce
  .map(([key]) => key)

console.log(output)

answered Mar 28 '20 at 06:34

Avin Kavish

8,317
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36

score 1 · Answer 3 · answered Mar 28 '20 at 06:38

This is sort of convoluted, but it works:

const prefer = {
  "c1": true,
  "c2": true,
  "c3": false,
  "c4": true
}

var setArray = ( prevArray ) => {
  return Object.keys(prevArray).filter(function(val, i) {
    if ( prevArray[Object.keys(prevArray)[i]] ) return Object.keys(prevArray)[i];    
  })
};

console.log( setArray(prefer) );

Adding elements in the array on the basis of an object

3 Answers3